Field of the Invention
This invention relates in general to filters, and in particular to a new and useful filter arrangement for cleaning the interiors of ventilated vehicles, which contains a coarse dust preseparator, a submicron particulate filter, and a gas filter.
Such filter arrangements serve primarily to clean vehicles or military vehicles which are used in regions contaminated with noxious substances of gaseous or particulate composition. The close quarters for the personnel to be protected or accommodated in such vehicles require a configuration of limited space for the respective filter elements.
In the known filter arrangements, the individual filters are each interchangeably installed in a common housing. Depending on the burden of dust particles or noxious gases in the outside air, the filters are replaced by new ones at varying times.
Because of the higher concentrations of dust occurring during driving of the vehicles, especially off the road, the submicron particulate filters are frequently clogged after a short time of operation. The gas filters always hold out longer, since the substances which they are intended to remove generally occur in small concentrations. Thus, up to the present, it has been necessary to replace the submicron particulate filters and gas filters separately.
Addition of a preseparator does not improve the situation, as this extends the need for replacement to three filter stages. It is now necessary to match three different separation efficiencies to an unforeseeable amount of noxious substances (DE-PS No. 26 35 860).